DNA methylation pattern of the SLC25A43 gene in breast cancer.

Solute carrier family 25A member 43 (SLC25A43) gene is a putative tumor suppressor gene that undergoes loss of heterozygosity (LOH) in human epidermal growth factor receptor 2 (HER2) positive breast cancer. Also, knockdown of SLC25A43 in cell lines influences cell turnover and metabolism. Absence of mutations in this gene in breast cancers prompted us to study methylation as an alternate mechanism for gene inactivation of this X encoded gene. Quantification of CpG site methylation using pyrosequencing was performed upstream of the SLC25A43 gene and at its 5' end in a cohort of breast tumor tissues (n = 80, HER2 positive or negative) with different SLC25A43 gene deletion status. Compared with control tissue, cancer tissues had lower levels of methylation at the 5' and 3' shores of the gene. Cancer tissues with no deletion in the SLC25A43 gene (Del (-)) had higher methylation in the CpG island (CGI) of the gene than cancers carrying the deletion (Del (+)). Methylation in the CGI of the SLC25A43 gene was negatively correlated with age at diagnosis. In HER2 positive breast cancer, ER negativity and lymph node positivity was associated with higher methylation in the CGI and in the adjacent shores of this gene. Our results suggest that methylation in the CGI of the SLC25A43 gene could be an alternate mechanism of gene silencing in the absence of LOH. Also, associations between site-specific methylation and clinicopathological parameters suggest that epigenetic changes in SLC25A43 gene could be of importance in breast carcinogenesis.